(a) Field of the Invention
The present invention relates to a manufacturing method of a solar cell.
(b) Description of the Related Art
A solar cell is a device that converts solar energy into electrical energy by photoelectric effect.
Today, much attention is paid to the importance of clean energy or next-generation fuel source, driven by increasing discussions about potentially negative effects of fossil fuel and green house effect from CO2 emissions. Discussions about the environmental impact of nuclear power generation and radioactive waste also fuel the general interest in clean energy.
In a solar cell, electric current is generated by two kinds of semiconductors, a P type semiconductor and an N type semiconductor. Typically, solar cells are classified into different kinds according to the material that is used as the light absorption layer.
Generally, the structure of a solar cell includes a front surface transparent conductive film, a PN film, and a rear surface reflecting electrode film that are sequentially deposited on a substrate.
If sunlight is incident on a solar cell having this structure, electrons are collected in an N layer and holes are collected in a P layer, generating electric current.
A compound solar cell (for example: a CIGS compound solar cell) is characterized by the fact that sunlight is converted into electricity without using silicon. A CIGS compound solar cell differs from the well-known silicon-based solar cell and offers a high efficiency. Copper (Cu), indium (In), gallium (Ga) and selenium (Se) compounds are deposited on an electrode that is formed on a flexible substrate, which may be made of stainless steel, aluminum and the like in addition to a glass substrate, to improve efficiency.
When the CIGS (Cu, In, Ga, Se) compound is deposited, evaporation or sputtering may be used.
In order to form the solar cell that has high efficiency, the ratio of copper (Cu), indium (In), and gallium (Ga) in the composition is optimized, crystallinity is increased, and defects between the interfaces are lowered.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.